Enabling logging on qemu/kvm VM

I'm running Cisco IOS-XRv-9000 sw on a qemu/kvm VM using Virsh on my linux Ubuntu system root@eve-ng62:/tmp# virsh list Id Name State ------------------------------------ 17 IOS-XRv-9000-carlo running root@eve-ng62:/tmp# From qemu monitor I turned on logging on cpu registers: (qemu) info version 6.2.0Debian 1:6.2+dfsg-2ubuntu6.26 (qemu) log cpu (qemu) logfile /tmp/qemu.log However I can't see any message stored in log file (/tmp/qemu.log). It basically remains empty: root@eve-ng62:/tmp# ll qemu.log -rw-rw-r-- 1 libvirt-qemu kvm 0 May 2 11:21 qemu.log root@eve-ng62:/tmp# Which could be the problem ?